Group III-V compound semiconductors such as, for example, GaN and AlGaN, are widely used for optoelectronics and electronic elements owing to many advantages such as, for example, a wide and easily adjustable band gap energy.
In particular, light emitting elements such as light emitting diodes or laser diodes using group III-V or II-VI compound semiconductors may realize various colors of light such as, for example, red, green, and blue light, as well as ultraviolet light, via the development of element materials and thin-film growth technique, and may also realize white light having high luminous efficacy via the use of a fluorescent material or by combining colors. These light emitting elements have advantages of low power consumption, a semi-permanent lifespan, fast response speed, good safety, and eco-friendly properties compared to existing light sources such as, for example, fluorescent lamps and incandescent lamps.
Accordingly, the application of light emitting elements has been expanded to a transmission module of an optical communication apparatus, a light emitting diode backlight, which may substitute for a cold cathode fluorescent lamp (CCFL) constituting a backlight of a liquid crystal display (LCD) apparatus, a white light emitting diode lighting apparatus, which may substitute for a fluorescent lamp or an incandescent bulb, a vehicle headlight, and a signal lamp.
In addition, light emitting diodes having excellent optical characteristics and a small size have recently been developed because the application thereof to light sources of, for example, portable appliances or lighting apparatuses is on the rise.
Although attempts have been made to form a pixel by reducing the cross-sectional area of a light emitting structure in order to realize a small light emitting diode, the thickness of each light emitting structure is too large to realize a super-thin-type unit pixel.
That is, the light emitting structure of the light emitting diode described above is grown on a substrate formed of, for example, sapphire. For example, in the case of a horizontal-type light emitting element in which the substrate remains after the light emitting structure is grown and a vertical-type light emitting element in which a metal support is coupled to one side of the light emitting structure and the substrate is removed, the substrate or the metal support is too thick to form a super-thin-type pixel.
In addition, a small light emitting element used in a super-thin-type pixel may be deteriorated in performance when the step coverage of a semiconductor layer or a metal layer, which is provided on a stepped portion, is poor.